The River Slope Mine, an anthracitecoal mine owned by the Knox Coal Company, flooded when coal company management had the miners dig illegally out under the Susquehanna River. Tunneling sharply upwards toward river bed without having drilled boreholes to gauge the rock thickness overhead, the miners came to a section with a thickness of about 6 feet (1.8 m) -- 35 feet (10.6 m) was considered the minimum for safety. The insufficient "roof" cover caused the waters of the river to break into the mine.

It took three days to plug the hole in the riverbed, which was done by dumping large railroad cars, smaller mine cars, culm, and other debris into the whirlpool formed by the water draining into the mine.

Twelve mineworkers died; 69 others escaped. Amadeo Pancotti was awarded the Carnegie Medal for being the first worker to emerge from the Eagle Air Shaft, which was the only exit available for 33 of those trapped underground. The bodies of the 12 who died were never recovered, despite efforts to pump the water out of the mine. The victims were Samuel Altieri, John Baloga, Benjamin Boyar, Francis Burns, Charles Featherman, Joseph Gizenski, Dominic Kaveliski, Frank Orlowski, Eugene Ostrowski, William Sinclair, Daniel Stefanides, and Herman Zelonis.

Eventually, an estimated 10 billion US gallons (38,000,000 m³) of water filled the mines. Ten people were indicted in the disaster's aftermath, including the mine superintendent, Robert Dougherty, owner Louis Fabrizio, secret owner August J. Lippi who was also the president of District 1 of the United Mine Workers, and three union officials. Six served jail time.

January 22, 2009, marked the 50th anniversary of the Knox Mine Disaster, with an annual memorial mass at St. John the Evangelist Catholic Church in Pittston Pennsylvania, and a ceremony held at the former St. Joseph's Catholic Church in Port Griffith, which is the site of a commemorative monument and a State Historic Marker, erected in 1999 by the Pennsylvania Historical and Museum Commission. The church was closed in May, 2008, due to a consolidation of area parishes, and put up for sale in July 2008. The property was purchased on January 15, 2009, exactly one week prior to the 50th anniversary, by Susan & John Baloga, the grandson of John Baloga, one of the 12 miners who perished in the tragic event. The property is now the site of Baloga Funeral Home Inc.. The 50th anniversary also included a special program at the Anthracite Heritage Museum in Scranton, which organized an annual program on the disaster in January.